Efficiency 4 + efficiency 3 in minecraft?

What happens when you forge efficiency 4 and efficiency 3 in the anvil zsm.

In minecraft pe

Nothing xD

Ef 4 or 5

4, so nothing happens except that your levels disappear, the book is gone and the anvil is damaged

Efficiency 4. It does not add up, but rather the highest one is selected.

It doesn't work at all. You can only do e.g. Efficiency 3 + 3, or 2 + 2 and so on.

Ok dk